Disk drives are widely used in computers, consumer electronics and data processing systems for storing information in digital form. The disk drive typically includes one or more storage disks and one or more head suspension assemblies. Each head suspension assembly includes a slider which has an air bearing surface, a leading edge, a trailing edge and a read/write head positioned near the trailing edge. The read/write head transfers information to and from the storage disk. Rotation of the storage disk causes the slider to ride on an air-supported journal bearing (also referred to as an “air bearing”) so that the read/write head is at a distance from the storage disk that is commonly referred to as a “head-to-disk spacing”.
Because today's disk drives utilize storage disks having increasingly high densities of data tracks, decreasing the head-to-disk spacing has become of great importance. However, this desire for a very small head-to-disk spacing must be balanced with tribological concerns in order to avoid damage to the read/write head and/or the storage disk, as well as loss of data.
Maintaining a relatively small and consistent head-to-disk spacing is further complicated by other factors. In particular, the read/write head includes a write head having an electrical conduction path, generally referred to as a “write element”. During a write operation, the electrical resistance of the electrical circuitry in the write element generates heat in and around the read/write head. A temperature increase causes thermal expansion of portions of the slider toward the storage disk, known as write pole tip protrusion (“WPTP”). In addition, environmental temperature increases within the disk drive that are independent of heating the write element and that act on a more global scale can also result in environmental pole tip protrusion (“EPTP”) in a direction that is generally toward the storage disk. If pole tip protrusion is excessive, the slider can unintentionally contact the storage disk (“head-to-disk contact”), causing off-track writing, degraded data transfer rates, damage to the slider, damage to the storage disk and/or a permanent loss of data.
Conversely, a temperature decrease in the drive will generally induce the opposite effect on the EPTP—the pole tips will retract from the disk. Such retraction can decrease the performance of the reading and writing process since larger spacing can generally degrade the information transfer to and/or from the disk.
Moreover, in conventional disk drives, the majority of the slider is often primarily formed from ceramic materials such as alumina titanium carbide (Al2O3—TiC), and can be secured to a suspension assembly that is typically formed from metal materials such as stainless steel. Environmental heat can cause deformation of the suspension assembly, which can result in a concave deformation of the slider. The concavity of the slider often occurs in a direction from the leading edge to the trailing edge, also referred to herein as the “crown” direction as temperature within the disk drive increases. This concavity results in the trailing edge, and thus the read/write head, moving closer to the storage disk, further risking or actually causing unwanted head-to-disk contact. Further, if the temperature of the read/write head decreases, the opposite effect can occur, e.g. the slider crown moves in the direction of being more convex (or at least less concave) resulting in an increase in head-to-disk spacing with potentially adverse implications, as indicated above.